The present invention relates generally to emergency control of brakes on locomotive consists (i.e. two or more interconnected locomotives) connected to a train of railroad cars.
A typical "train consist" includes at least one locomotive connected to one or more rail cars and a plurality of "trainlines" extending between the respective cars and between the locomotive and the cars. Trainlines comprise both pneumatic and electrical lines that interconnect air brakes and electrical devices respectively located on and/or in each of the cars. In the locomotive, the pneumatic trainline includes a brake actuating pipe, a main equalizing reservoir(MER) pipe and an independent application and release (IAR) pipe. Within the "locomotive consist", each of the MER, brake actuating and IAR pipes respectively interconnect with the MER, actuating and IAR pipes of the other locomotive(s). These are the pipes that serve to supply pressurized air to pneumatic brakes situated on each of the locomotives of the consist.
From a lead locomotive to the first car of the train and from the first car to the last car of the train, the pneumatic trainline includes a brake pipe having a pressure that mimics the pressure within an equalization tank and reservoir located in the lead locomotive. The brake pipe itself includes a series of pipe lengths secured to the underside of the cars, the lengths being connected together via flexible coupling hoses situated between the cars.
Sometimes referred to in the singular as a "trainline" or "trainline cable", electrical trainlines, i.e., wire conductors, include a power line, a return (ground) line and various control and other electrical lines contained within a protective sheath or conduit.
A typical locomotive consist uses an electronic brake control system such as the WABCO EPIC.RTM. equipment, as described in U.S. Pat. Nos. 5,192,118 and 5,222,788. The disclosures of these patents are incorporated herein by reference. In using the EPIC.RTM. equipment in a locomotive consist, one of the locomotives of the consist is equipped as the control locomotive, which locomotive remotely operates the brakes of slave locomotives of the consist. In addition to EPIC.RTM. and other electronic brake control systems, a locomotive consist may be provided with distributed electrical power control equipment which uses radio transmitting and receiving equipment to control slave locomotive(s) located near or at the center of the overall length of the train or to locomotive(s) at the end of the train remote from the controlling locomotive.
The cab of a typical locomotive includes an independent brake valve handle, an automatic brake valve handle, and an electronic cab control unit. The cab control unit has a CPU board and an input/output (I/O) card which links the handles to a cab CPU board. Through use of the independent brake handle, a train operator may apply and release the brakes on the locomotive consist. Through the automatic brake handle, the train operator may apply and release the brakes not only on each locomotive but also the brakes on each rail car, the handles being effective to control pressure in the brake pipe. The reduction or increase of pressure within the brake pipe, and thus the amount of braking power exerted by the train brakes, generally corresponds to the position of the automatic brake handle.
A cab control unit supplies to a cab brake control unit signals representing the positions of the automatic and independent brake handles. The automatic brake handle may be moved to and between any of the positions described generally as follows. From a release position, at one extreme, in which brake pipe pressure is maximum and the brakes are completely released to an emergency position, at another extreme, in which brake pipe pressure is at an approaching zero and the brakes are fully applied, the brake pipe may assume any pressure level in between. When the automatic brake handle is moved to the release position, the brake equipment increases pressure within the equalization reservoir and in the brake pipe and correspondingly reduces pressure within the brake cylinders so as to release completely the train brakes. In the minimum service position, the brake equipment reduces pressure slightly in the equalization reservoir and thus in the brake pipe so as to provide a minimum application of the brakes rather than having no application with the full release position. In the full service position, the brake equipment further reduces pressure within the equalization reservoir and thus the brake pipe and correspondingly increases pressure within the brake cylinders so as to apply fully the train brakes.
In a continuous service position, the brake equipment reduces the equalization reservoir pressure to zero at a preset service rate of reduction. When the automatic brake handle is moved back into a service zone situated between the minimum and full service positions, the brake equipment generally holds pressure within the brake pipe at the currently existing pressure. In the emergency position, the brake equipment exhausts brake pipe pressure to atmosphere through emergency magnet valve(s) at an emergency rate so as to apply quickly and fully the train brakes.
Likewise, the independent brake handle may be moved between and placed within any of two positions. When the independent brake handle is moved to the release position, the brake equipment reduces pressure within the IAR pipe and correspondingly reduces pressure in the brake cylinders of the locomotive so as to release completely the locomotive brakes. Similarly, when the independent brake handle is moved to the apply position, the brake equipment increases pressure within the IAR pipe and correspondingly increases pressure in the brake cylinders of the locomotive so as to apply fully the locomotive brakes. Pressure within the IAR pipe and the locomotive brake cylinders reduces and increases in relation to the position of the independent brake handle.